Watch movement demagnetizing apparatus



June 10, 1958 F. DosTAL WATCH MOVEMENT DEMAGNETIZING APPARATUS 2Sheets-Sheet 1 Filed Oct. 24, 1955 /N VEN ro@ FRA l( OOST/1l.

June 10, 1958 F. DosTAL 2,838,720

WATCH MOVEMENT DEMAGNETIZING APPARATUS Filed Oct. 24, 1955 2Sheets-Shea?, 2

/9 i 1 /5 1J/5 i /6 7l /7 /72 DRT/9U" I4 Q/5 I4 s jl' i [SVT 6 L |I UTF/N VEN Tol? RA United States Patent WATCH MOVEMENT DEMAGNETIZINGAPPARATUS Frank Dostal, Great Neck, N. Y., assig'nor to American TimeProducts, Inc., New York, N. Y., a corporation of Delaware ApplicationOctober 24,1955, Serial No. 542,204 1 claim. (ci. S11-157.5)

The instant invention relates to an eliminator of magnetic effects inwatch movements and parts thereof.

An object of the invention is to provide al demagnetizer for watchmovements which is simple, quick and effective in operation andeliminates all uncertainty on the part of the user such as are presentlyinvolved with prior devices.

A further object is to provide a watch movement demagnetizer whichappreciably reduces the time required for the demagnetization ascompared to prior art devices.

A further object is to provide a watch movement demagnetizer whichoperates at a frequency which cannot damage any part of the watchtested, while operating at energies which are a large multiple of theprior art devices.

The foregoing, aswell as other, objects as also the features andadvantages of the invention will become apparent in the course of thefollowing detailed description of an illustrative embodiment shown inthe accompanying drawing, in which:

Figure 1 is a top View of an illustrative embodiment of the watchdemagnetizer of our invention;

Figure 2 is a side elevation thereof;

Figure 3 is a section through the demagnetizing coil of our device; and

Figure 4 is a circuit schematic of our watch demagnetizer.

Referring to the drawing, the demagnetizer of my invention is housed ina rectangular container 1 open at its base, which may be closed by afitted bottom 2. The top 3 of the container has a large opening 4 whichis of such size as to be larger than the average watch, for example 3%long and 2%" Wide for a container 61/2 long and 5" wide, which is closedby a dielectric sheet 5 affixed to the inner surface of the top and isfor example of a grass-base Baia-elite or other non-magnetic out mcchanically rigid material. The opening 4 has aligned therewith amulti-turn coil 6 of enameled Wire wound on a formed core 7 of magneticmaterial, such as compressed iron powder. As shown in Figure 3, the core7 is cup-shaped having a rim 8 and a center post 9 integral with itsbase. The lmulti-turn coil 6 is wound on a cylinder 1i), of cardboardfor example, and is of such height that the coil height is somewhat lessthan the depth of the annular recess 11 between the rim 8 and the centerpost 9, and of an outer radius somewhat less than the inner radius ofthe rim. A small aperture 12 through the core base permits the ends ofthe wire of the coil to be drawn therethrough to make the requiredcircuit connections. By way of example in one embodiment the core 7 isof outer diameter of 2%", in height, the center post 9 being l" indiameter and the rim 9% wide, radially, with the free ends of the postand rim coplanar, the outer diameter of the coil is 1% and the depth ofthe recess 11 is 1/2.

The core 7 is supported in a panel 13 so as to project therefrom towardthe sheet 5 closing the opening 4 with 2,838,720 Patented June 10, 1958ICC the free face of the rim 8 and center post 9 closely adjacentthereto, the panel 13 in turn being supported in any well known mannerfrom the container side walls. While in one embodiment of thedemagnetizer the container 1, the bottom 2 and the panel 13 are of wood,any suitable non-magnetic material, such as various of the plastics, ormetals, may be used. On its face opposite to that from which the core 7projects, the panel 13 also supports the rectifier elements 14 and thecapacitors 15 together with their connections, the electricalconnections having been omitted in Figures l and 2 for simplicity ofillustration, which are connected to constitute a voltage multiplier,specifically a quadrupler in this embodiment. Also supported on suchface of panel 13 is the charging resistor 16 through which the capacitor18 is charged. The spring-biased push button switch 173 is mounted inthe top 3 at a convenient region thereof other than the opening 4.Similarly a pilot light 19, connected across the supply line, is mountedin top 3.

The wiring diagram of the demagnetizer of my invention is shown inFigure 4, with the elements in the dashed box 2() indicating a voltagequadrupler of any Wellknown prior type in which one output terminal isconnected through the charging resistor 16, which prevents overloadingthe voltage quadrupler, to a fixed contact 171, engageable by switch 17,and normally engaging therewith, the other output terminal of thevoltage quadrupler being connected to one side of capacitor 18 of whichthe other side is connected to the terminal on which switch 17 pivots.The ends of coil 6 are connected respectively to fixed contact 172engageable by switch 17 but normally disengaged therefrom, and the sideof capacitor 18 connected directly to the voltage quadrupler output.Switch 17 is biased by a spring so that normally the charging circuit2i), 16, 171, to capacitor 18 is closed, while on depressing button 173against the spring biasing switch 17, such charging circuit is openedand the discharge circuit 172, 6, 18, is closed, discharging thecapacitor 18 through coil 6. On releasing switch button 173, the switch17 is immediately returned to terminal 17, under the influence of itsspring to open the discharge circuit and close the charging circuit. Onthe passage of the current through coil 6, the oscillatory circuitcomprising coil 6 and capacitor 18 will oscillate for a short interval,of perhaps 1/30 second, at a frequency as determined by the constants ofsuch circuit, which frequency is damped from its initial peak amplitudeto a final minimum approaching zero. But with the core 7 cup-shapeddescribed, the center post 9 and the rim 8 will be the opposite poles ofan electromagnet so formed, with the polarity of each rapidly reversingat the oscillating frequency. Thus when placing a watch, either face upor face down but preferably the latter as indicated by the dashed lines21 in Figure 3, on the sheet 5 within the opening 4, the magnetic linesof iiux passing through the watch movement from the center post 9 to therim 8 in rapidly reversing directions and at a decaying intensity, willdemagnetize the watch. The line supply connecting wires 22 areconveniently passed from the interior of the container through anaperture 23 in the bottom 2. The latter is affixed to the container, forexample by screws 24, and has rubber casters 25 on its outer surface onwhich the assembled unit rests.

'While the voltage multiplier 2t) shown in Figure 4 is shown as avoltage quadrupler, and hence for a line voltage of 11G-120 volts at 60C. P. S., will result in a charging voltage of some 440 to 6(10 voltsfor the capacitor 18, it is obvious I do not limit myself to just thistype of fourfold multiplication of the available line supply. l havefurthermore determined that the frequency of the oscillatory circuit,coil 6 and capacitor 18, is not critical although I prefer to have suchfrequency above 200 cycles per second to eliminate all danger of injuryto parts of the watch movement. Winding the coil 6 with enameled copperwire of number 26 gauge and to the dimensions above given, and withcapacitor 18 of some 4 uf., the frequency is some 500 C. P. S. and ismost satisfactory. I have also found that a time interval of some fiveseconds between successive operations of the switch 17 is advisable togive the capacitor 13 ample opportunity to be recharged after adischarge. Y

It will be noted that the demagnetizing operation of a watch with theinstant demagnetizer is simple in that,

the demagnetizer having been connected to the supply line, the watch isplaced, preferably with its Vface down as above stated, on the sheet 5and the button 173 pressed and then released. Complete demagnetizationis thus a matter of 1750 of a second or so, as compared to severalseconds with prior art devices. The latter generally included a coil,energized by a key maintained in closed position from the electric line,and the watch ap proached axially to the coil and then withdrawn alongthe coil axis to a distance of a foot or more from the coil. The user ofthe prior art devices always feared that he might have not manuallyapproached and withdrawn the watch truly along the axis of the coil,particularly in withdrawal was it difficult to avoid deviating from suchaxis, thereby subjecting the Watch to the decreasing ac- What I claimis: Y

A demagnetizing apparatus for watch movements and cased watchescomprising a housing, a voltage multiplier adapted to be connected to anA. C. potential supply, a resistor connected to one output terminal ofthe multiplier, a capacitor connected at one side to the other outputterminal of the multiplier, 'a cylindrical core of compressed powederediron of highpermeability integral with a cup of the same material havinga cylindrical wall concentric with the core, a multi-turn coil about thecore and substantiallyrlling the cup space between the cylin drical cupwall and the core and having one end connected to that side of thecapacitor connected to said multiplier output terminal, the multiplier,resistor, capacitor, core with .integral cup and the coil being disposedwithin the housing, a switch operable from the exterior of the housingand supported in a Wall of the housing and connected to the other sideof the capacitor and normally connecting the resistor to the capacitorand operable to disconnect the resistor from the capacitor and connectthe other end of the coil to the capacitor, the housing having anaperture aligned with the core with integral cup and the coil, and asupporting means of a material permeable to magnetic lines of force overthe aperture,

on which supporting means the watch movements and cased watches to bedemagentized are positionable, the tops of the core,rcoil and the cupwall being coplanar and closely adjacent to the watch supporting means.

References Cited in the file of this patent UNITED STATES PATENTS KuehneJan. 18, 1955

